In a traumatic day for the SNP, Nicola Sturgeon, the Deputy First Minister, dropped a taxpayer-funded court action preventing the disclosure of whether ministers hold legal advice on an independent Scotland’s EU status.

Paul Martin, a Labour MSP, said: “It appears the First Minister is a liar and used taxpayers’ money to try to cover up his lies.

“Now Nicola Sturgeon has confirmed that Alex Salmond never had any advice to keep secret in the first place. Alex Salmond has started the debate on Scotland’s future within the UK with barefaced lies that even embarrass his deputy.”

Ruth Davidson, the Scottish Tory leader, said: “This has been a Cabinet cover-up right from the beginning using taxpayers’ money to try and hoodwink the Scottish people.”

The row centred on an interview Mr Salmond gave in March this year in which Andrew Neil, the BBC political journalist, asked whether he had sought advice from law officers on an independent Scotland being an EU member.

“We have, yes, in terms of the debate. I can’t reveal the legal advice of law officers but what you can say is everything we publish is consistent with the legal advice we receive,” the First Minister said.

Among the documents published were a parliamentary answer in November last year which stated “an independent Scotland would not be forced into adopting the euro” and would continue in the EU.

But Miss Sturgeon told the Scottish Parliament yesterday that the Scottish Government had “not sought specific legal advice” on the issue.

The Deputy First Minister announced that the advice had now been requested, but only after the signing of last week’s deal with David Cameron to hold the independence referendum.

She said SNP ministers have dropped a legal action against Scotland’s information commission, who had ordered that they disclose whether the advice existed.

However, at least £12,000 of taxpayers’ money has already been spent on the action. Mr Salmond was forced to return to the Holyrood chamber last night to deny he was a liar.

The First Minister told MSPs he was not referring to specific legal advice on EU membership during the BBC interview.

Instead he claimed he was merely stating that all the Scottish Government’s publications are underpinned by legal advice.

He said Labour’s “barefaced liar” accusation was based on a transcript of the interview that omitted 27 words.

But Willie Rennie, the Scottish Liberal Democrat leader, said Mr Salmond had replied in the affirmative to a “straightforward question” on the existence of legal advice.

“The First Minister has not cleared up the matter,” Mr Rennie said. Mr Neil tweeted there "was no confusion" that his question was referred to legal advice about EU membership.

Alistair Darling, the former Chancellor who is leading the Better Together referendum campaign, said: “This strikes at the heart of Alex Salmond’s credibility.”

Meanwhile, the Scottish Government finally published an analysis of the 26,000 responses to a public consultation held on the referendums rules.

In a further blow to the First Minister, this showed 62 per cent wanted a single, straight question on independence and more individual respondents (50 per cent) oppose giving the vote to 16 and 17-year-olds than support the move (48 per cent).

Opinion was also split about holding the vote on a Saturday, as Mr Salmond has suggested, with 47 per cent agreeing and 31 per cent opposed.